He's wasted sitting deep though and is ineffectual. Last night was proof. He was non-existent in the first half as he sat deep. In the second half he started driving forward and Bob's your uncle, he looked threatening throughout and the Croats were a vastly improved team because of it.
He won't be ineffectual at United. He'll be effective at spreading play. In any case, we can play more than one formation, and certain players won't play every game, meaning he can play further forward too.